Online ISSN: 0024-9637
Climate diagrams o f monthly temperature and precipitation data. Stippled areas are periods of relative water deficit; striped are periods o f water surplus, a) Long-term averages for Todos Santos, Baja California Sur, MX (1 9 2 1-1 9 6 7 ; data from Todos Santos weather station; Hastings and Humphrey 1969). b) Desert Botan­ ical Garden monthly values from December 1991 to September 1993. Data are from the Tempe, Arizona, U SA weather station, 2 km SW (Arizona Climate Summary, Office o f the State Climatologist for Arizona).
To examine the physiological adaptability of Encelia farinosa var. phenicodonta from southern Baja California, plants from Todos Santos, BCS were raised in central Arizona where winter-spring precipitation is greater than typically experienced by this variety. Plants were capable of high photosynthetic rates during the cool and wet spring months and showed substantial growth and reproductive output. Winter freezes caused severe stem dieback and even plant death. These findings suggest that freezing temperatures may influence the restricted and disjunct distribution of E. farinosa var. phenicodonta in the northern part of its range. The growth and reproduction results also imply that this variety may possess the physiological adaptability to thrive under potential climatic changes in southwestern North America. Journal Article
The moss flora of Lake County, California comprises of 300 species and one variety within 111 genera. This represents 44 percent of the California moss flora occupying an area less than one percent of the state land area. Six species, Bryum veronense De Notaris, Gemmabryum kunzei (Hornschuch) J.R. Spence, Schistidium flaccidum (De Notaris) Ochyra, Tortella alpicola Dixon, Trichodon cylindricus (Hedwig) Schimper, and Trichostomum brachydontium Bruch were documented as new for California. Four species, Acaulon mediterraneum Limpricht, Funaria convexa Spruce, Gymnostomum viridulum Bridel and Schistidium echinatum Ignatova & H.H. Blom, were documented as new records for the North American moss flora. During this study, thirteen species were described as new to science with at least one occurrence documented from Lake County: Didymodon californicus J.A. Jiménez, D.R. Toren & Shevock, D. eckeliae R.H. Zander, D. norrisii R.H. Zander, Gemmabryum vinosum J.R. Spence & Kellman, Grimmia serrana Muñoz, Shevock & D.R. Toren, G. torenii R.I. Hastings, Homalothecium californicum Hedenäs, Huttunen, D.H. Norris & Shevock, Imbribryum torenii J.R. Spence & Shevock, Orthotrichum persimile F. Lara, R. Medina & Garilleti, Ptychostomum pacificum J.R. Spence & Shevock, Schistidium splendens T.T. McIntosh, H.H. Blom, D.R. Toren & Shevock, S. squarrosum T.T. McIntosh, H.H. Blom, D.R. Toren & Shevock and Scleropodium occidentale B.E. Carter.
Signed at end: Mrs. W. Winslow Crannell.
An exceptional dataset for over 12,000 Carnegiea gigantea collected by the Arizona Department of Game and Fish over two field seasons on a restricted military reservation was released to the authors for analysis, including a variety of variables for which little empirical evidence exists. Data on epidermal browning, physical damage due to fire, lightning, gunshot or topping, rodent girdling, bird cavities and other variables were assessed using primarily chi-square analysis. The main findings of this study include: (1) Plants with high amounts of epidermal browning were rather evenly distributed across height classes, although the very smallest plants (0–0.9 m) had substantially less epidermal browning. (2) Although past work has shown that epidermal browning is surely a function of solar radiation receipt, other variables (bird cavities, girdling, damage, branching) are statistically linked with browning, raising the possibility that other biotic and abiotic factors may hasten browning. (3) Bird cavities are better predicted by height than branches, likely due to decreased visibility and exposure to thermally tempering winds caused by branches, and improved defensive position and reduced exposure to heating from the surface associated with taller plants.
Location of sampled regenerating stands and old-growth reference sites in Mendocino County, California.
STAND CHARACTERISTICS OF SIX AGE-CLASSES IN A CHRONOSEQUENCE OF POST-HARVEST DEVELOPMENT IN THE CENTRAL RANGE OF THE SEQUOIA SEMPERVIRENS FOREST. Age-classes sharing the same lower-case letter in each series were not significantly different, based on single factor ANOVA analysis (a 5 0.05).
Percent cover of trees, shrubs, and herbs on six age-classes on a post-harvest chronosequence in the central range of the Sequoia sempervirens forest; error bars indicate standard error.  
Principle components for plant species across a 127-yr chronosequence of naturally regenerating Sequoia sempervirens stands. PC-1 explained 35.9% of variation. PC-2 explained an additional 17.4%. Convex outlines indicate post-harvest and old-growth age classes.  
REDWOOD FOREST. The estimated date of introduction is based on the earliest specimen records for each species in northern coastal California, retrieved from the Consortium of California Herbaria ( cgi-bin/get_consort).
Understanding the natural patterns of regeneration following human disturbance is essential for effective restoration and management of second-growth forests. Despite their unique ecological character, little is known about these patterns in Sequoia sempervirens (D. Don) Endl. (Coast Redwood) forests. We examined the composition and structure of naturally regenerating stands with 360 randomly located sample plots across a chronosequence of five replicated age-classes (18 to 127 yr) and three old-growth reference sites. Results indicate a progression of stand characteristics towards old-growth conditions, with several measures reaching old-growth equivalence within the timeframe of the chronosequence. Stand density, canopy cover, and species richness reached old-growth equivalence within 41-80 yr; Shannon-diversity reached old-growth equivalence between 80-100 yr; and the density of redwood seedlings and shrub cover reached old-growth equivalence between 100—130 yr. Basal area, herb cover, and the relative dominance of S. sempervirens progressed toward, but did not reach, old-growth equivalence. Size-class analysis indicated an increase in the density of large diameter trees, with no change in the density of smaller size-classes after forty yr. Coast redwood associated understory species were favored on the older sites with the cover of Calypso bulbosa (L.) Oakes, Trillium ovatum Pursh, and Viola sempervirens Greene reaching old-growth equivalence, while Iris douglasiana Herb., Tiarella trifoliate L., and Achlys triphylla (Sm.) DC. did not. No non-native species were recorded in stands older than 60 yr. We conclude that coast redwood forests are resilient to human disturbance, though some old-growth characteristics may require more than a century to develop.
Vegetation structure, composition, and community patterns on the landscape of southwest Oregon have changed since Euro-American settlement began in the mid-1800s. Much of this change has been attributed to the transition of land management strategies from those dominated by Native American practices, through the early Euro-American settlement period, and on to the post World War II era of industrial scale timber harvest and fire suppression. Using homestead patent applications and associated land classification maps generated under the Forest Reserve Homestead Act of June 11, 1906, we add to the understanding of historic vegetation conditions and evaluate vegetation change over time for land applied for by homesteaders in the Applegate River watershed of southwest Oregon. These homesteads were predominately located on areas now supporting chaparral, Pinus and/or Quercus woodlands, mixed conifer forests, pastures, and agricultural land. Our study presents primary source documentation that describes stands dominated by broadleaf trees and shrubs as dense at the time of patent application, contrary to the assumption that such stand structures are an artifact of fire suppression efforts of the last century. Historic vegetation polygons cross tabulated with current classified imagery in GIS indicate that conifer forests and shrublands each retain most of their former extents within their same locations on the landscape. The persistence of shrub stands to current times implies longer-term stability of these communities and indicates that a transition to conifer domination is not evident in all shrublands.
Two of the most used sources for distributions of cacti (Cactaceae) indicate the family's northern range limit is either 58°N or 58°15′N for Opuntia fragilis. However these sources overstate the range limit by almost two degrees, an error that probably originated as a simple misreading of the latitude of Fort St. John. I discuss records of O. fragilis at and just south of 56°17′ N along the Peace River valley between Fort St. John, British Columbia and Peace River, Alberta, as well as why it is surprising but unlikely that specimens currently exist farther north. An error in latitude of 2° (223 km) in range can adversely affect ability to empirically estimate effects of climate change.
Flowering phenology in five chaparral species was investigated using more than a century of data obtained from herbarium collections. Three species examined were from the genus Arctostaphylos (Ericaceae) and two from Ceanothus (Rhamnaceae). Collections of these species were examined relative to climate change data during the same time period. For all the species, no change in average flowering time occurred during the past century. Considerable variability was found in flowering phenology and this variability was explored using generalized linear (GLM) and generalized linear mixed models (GLMM) and different dimensions of temperature and precipitation timing. While the genera performed differently, both required combinations of precipitation, temperature, and their interactions to predict flowering date. Arctostaphylos responded the most to precipitation interactions, while Ceanothus responded the most to temperature interactions and the previous growing season's precipitation. In both genera, regression coefficients were combinations of both positive and negative variables, indicating that flowering dates are complex interactions among the different dimensions of precipitation and temperature.
Location of tanoak study sites and experimental block layout. A. Location of the study site in southern Humboldt County, California. B. Aerial photograph showing the location of blocks. C. Experimental layout of each block after simple randomization of treatments. Control plots were positioned in the center of each block and experimental plots (N 5 'non-girdled', F 5 'fully-girdled', H 5 'half-girdled') were randomly assigned. D. Layout of plot design showing the grid method used for establishing two, 6 m transects for collecting soil and roots positioned towards the center of the plot. 
Ectomycorrhizal hyphal abundance from roots and soil five (June 2003), nine (October 2003) and thirteen (February 2004) months after girding Notholithocarpus densiflorus trees. Mean hyphal abundance for each treatment (+1 SE) are graphed. Girdling decreased the ectomycorrhizal soil hyphal abundance did not similarly affect root hyphal abundance. 
Root and soil hyphal abundance of Cenococcum and Tricholoma five (June 2003), nine (October 2003) and thirteen (February 2004) months after girding Notholithocarpus densiflorus trees. Means (+1 SE) are graphed. A. Cenococcum root hyphal abundance. B. Tricholoma root hyphal abundance. C. Cenococcum soil hyphal soil abundance. D. Tricholoma soil hyphal abundance. A significant taxon 3 time interaction was observed for ectomycorrhizal root hyphal abundance but not for soil hyphal abundance. 
Invasive plant pathogens are often recognized as serious threats to the maintenance of biodiversity affecting both structure and function of ecosystems. Here, we investigate the potential impact of the invasive pathogen Phytophthora ramorum Werres, de Cock & Man in't Veld by using physical girdling of tanoak, Notholithocarpus densiflorus (Hook. & Arn.) Manos, Cannon & S. H. Oh (Fagaceae), as a surrogate for the disease and to test for changes on the hyphal abundance of ectomycorrhizal fungi. In this study, the flow of phloem to the roots of girdled trees was severed by cutting two narrow incisions (about 10 cm distant) through the inner bark around the circumference of the stem of each tree (fully-girdled), or by cutting two narrow incisions half of the circumference of the tree (half-girdled), to compare with untreated (non-girdled) trees. The hyphal abundance of two common and ecologically important ectomycorrhizal genera (Cenococcum and Tricholoma) was estimated from the roots and surrounding soil using real-time PCR quantification (TaqMan) assay. A significant decrease in the hyphal abundance from soil was observed in girdled tree plots. In contrast, no similar decrease in the root hyphal abundance was observed. Ectomycorrhizal fungi have a major impact on ecosystem function through their control over decomposition, nutrient acquisition, and mobilization and regulation of succession in plant communities. Given their important function, the decline in EM abundance of tanoak infected by P. ramorum will likely disrupt the function and structure of these forests.
Seasonal differences. A-D. Percent fruits lost during the season. Because sample size varied by season, values do not sum to 100. E-H. Number of fruits lost per plant and per day. I-L. Percent of fruits lost per plant and per day. M-P. Percent of the fruits remaining at the end of the season that are healthy. Samples sizes are number of year-site combinations. Graphs do not match results in Table 2 exactly because they show averages for all sites, whereas in Table 2 comparisons are limited to sites where data for both years were available.
Number of fruits lost per plant and per day by region and by Julian date. Data points are site means. Shaded area indicates the 95% confidence interval around the regression line. Results of the analyses can be found in Table 3.
Changes in percentage of fruits in a healthy state over the course of the fall period. Data points are site means. Values on the y-axis are back-transformed from an arcsin square-root transformation; the axis is not linear. Shaded area indicates the 95% confidence interval around the regression line. Results of the analyses can be found in Table 3.
SITE LOCATIONS AND DESCRIPTIONS. S ¼ School. Species abbreviations: Empnig ¼ Empetrum nigrum, Rosaci ¼ Rosa acicularis, Vacvit ¼ Vaccinium vitis-idaea, Vibedu ¼ Viburnum edule.
EFFECT OF JULIAN DATE, ECOREGION, AND THEIR INTERACTION ON NUMBER OF FRUITS LOST PER DAY (NUMLOST), PERCENT OF FRUIT LOST PER DAY (PERLOST), AND PERCENT OF FRUIT THAT ARE HEALTHY (PERHEALTHY) IN FALL. Values in bold indicate significant differences following a Benjamini-Hochberg procedure with a false discovery rate of 0.05.
Plants with persistent fleshy fruits that last throughout fall and into winter and spring are an important source of nutrition for animals and people in boreal, subarctic, and arctic regions, but little information on fruit retention or loss is available for these regions. We evaluated fruit loss for four species across Alaska using data from our Winterberry community science network. Plants of Rosa acicularis Lindl., Viburnum edule (Michx.) Raf., Vaccinium vitis-idaea L., and Empetrum nigrum L. were monitored on a weekly basis throughout fall until snow cover and again after snow melt in 24 communities in six ecoregions in 20162020. Observers counted fruits and classified them into unhealthy (dried, rotten, or damaged) or healthy. Number of fruits lost per day (absolute loss rate) decreased over the course of the fall, but percent of fruits lost per day (relative loss rate) was constant for all species except E. nigrum, where it declined throughout the fall. Rates of loss were similar across ecoregions and climatic gradients, although for V. vitis-idaea the two most southern sites had the lowest relative loss rates and for E. nigrum the sites warmest in summer had the lowest loss rates. Fruit loss pulse events (>15% fruits lost in one week) were uncommon (<5% of weekly observations). At the time of persistent winter snow cover, plants retained 2550% of fruits, with higher retention in more southern ecoregions. During winter, both relative fruit loss and absolute fruit loss rates dropped compared to fall, but in spring they rebounded to fall levels. Low proportions of unhealthy fruits in E. nigrum and V. vitis-idaea were in part due to rapid abscission of unhealthy fruits, while the other two species tended to retain unhealthy fruits. We estimate that vertebrate frugivores obtain 645 as many fruits in fall as do decomposers / invertebrates. The higher loss rates during the snow-free seasons and constant rates of fruit loss for most of the focal species and locations suggest that longer falls and earlier fruit ripening will lead to lower fruit availability to animals in winter and spring.
The seasonal mean (61 SE) leaf pressure potentials at predawn (A-C) and midday (D-F) for two Pinus taxa, P. ponderosa and P. arizonica, from sites at three different elevations (High, Mid, and Low) across three seasons (Arid foresummer, Summer monsoon, and Winter). For panels A, C, D, and F, bars with different lowercase letters are significantly different. There were no significant differences among taxa and sites for the data shown in panels B and E.
Vulnerability to cavitation curves for two Pinus taxa, P. ponderosa and P. arizonica, with the decline in mean (61 SE) xylem specific conductivity (K s ) with pressure for three different sites: (A) a high elevation site containing only P. ponderosa compared to a low elevation site containing only P. arizonica, and (B) a mid-elevation site where both taxa cooccur.
PREDAWN AND MIDDAY LEAF PRESSURE POTENTIALS (MPA; MEAN 6 1 SE) FOR TWO PINUS TAXA, P. PONDEROSA AND P. ARIZONICA, FROM SITES AT THREE DIFFERENT ELEVATIONS (HIGH, MID, AND LOW) ACROSS THREE SEASONS (ARID FORESUMMER, SUMMER MONSOON, AND WINTER). Each taxon only occurred across two of the sampled elevations, and N/A is reported if a taxon did not occur at a given site. Significant differences between sites and species within a season are shown in Fig. 1.
The ability of plants to tolerate and recover from periodic water stress affects their competitive ability, survival, and distribution, leading to shifts in plant communities as environmental conditions change. We investigated the hydraulic traits of two closely related Pinus taxa to assess population and taxonomic variability in plant hydraulic traits. We hypothesized that traits would vary with elevation but exhibit similar traits where taxa co-occurred. We measured predawn and midday leaf pressure potential (Wp) across three seasons, xylem specific hydraulic conductivity (Ks), and vulnerability to xylem embolism (P50). These were measured on Pinus ponderosa var. brachyptera (Engelm.) Lemmon that occurred at a high elevation site (2770 m), P. arizonica Engelm. at a low elevation site (2135 m), and both species where they co-occurred at the midelevation site (2475 m) in the Santa Catalina Mountains of southern Arizona. Plants from the high elevation site had the least negative Wp and the highest Ks. The two taxa differed from one another when compared between the high and low elevation sites, but they were not different where they co-occurred. The two Pinus taxa show plasticity in their hydraulic traits across sites. Conditions across the elevational gradient appear to lead to a convergent solution in hydraulic traits for these taxa where their ranges overlap but differences in traits where they do not overlap. Increasing aridity in the region could lead to shifts in suitable habitat, reduced water transport ability at range margins, and shifts in population distributions.
The bryoflora of the Russian Wilderness and adjacent slopes, an area of 112.8 mi2 (292 km2), comprises only 1.8% of the land base of Siskiyou County at 6347 mi2 (16,439 km2), the fifth largest county in California. Fifty liverworts and 215 mosses (includes four undescribed taxa) are documented by voucher specimens. This represents 33% for both the liverworts and the mosses documented for California. Three species, Lophozia longidens (Lindb.) Macoun, Lophozia obtusa (Lindb.) A.Evans, and Solenostoma schusterianum (J.D.Godfrey & G.Godfrey) Va, Hentschel & Heinrichs are reported as new for California. Grimmia brevirostris R.S.Williams is elevated from synonomy with Grimmia hamulosa Lesq., as a species worthy of recognition and represents the first records of this California endemic for the Klamath Ranges.
The taxonomically difficult and ecologically and phytogeographically important genus, Calamagrostis, was examined for British Columbia (BC). Morphological characters were analyzed by Principal Components Analysis (PCA) to characterize taxa and to aid in the development of a new key. Eight native species (Calamagrostis canadensis, C. lapponica, C. montanensis, C. nutkaensis, C. purpurascens, C. rubescens, C. sesquiflora, and C. stricta) are confirmed to occur in British Columbia, of which C. montanensis, C. nutkaensis, C. purpurascens, C. rubescens, and C. sesquiflora are reliably distinguishable. Comparison of species distribution to regional climatic and vegetation history suggests that Calamagrostis nutkaensis and C. sesquiflora likely survived in coastal refugia during late Wisconsin glaciations. Calamagrostis purpurascens likely persisted beyond the glacial limits or within nunataks and then spread into previously glaciated sites. Two interior continental species, C. montanensis and C. rubescens, probably spread north and west from the unglaciated zone south of the Cordilleran and Laurentide ice sheets. Calamagrostis lapponica likely persisted north of the ice sheets, and then spread southward into high-elevation sites in northern and eastern BC. Calamagrostis canadensis and C. stricta probably survived south and north of the ice sheets, and then spread into the previously glaciated terrain.
Tanoaks, Notholithocarpus densiflorus (Hook. & Arn.) Manos, Cannon & S. H. Oh, are being killed by sudden oak death, caused by the pathogen Phytophthora ramorum Werres, de Cock & Man in't Veld. However, very little is known about the basic ecology of the species. Here we investigate the pollination ecology of tanoaks using insect-visitor observations along with a pollinator-exclusion study. Insect-visitor observations were conducted by citizen-scientist volunteers at three different sites in the Midpeninsula Regional Open Space District lands in the Coast Range of California in 2009. Pollinator exclusions were conducted over two years (2009, 2010), using veil bags to prevent insects from reaching female flowers at the Blodgett Forest Research Station in the Sierra Nevada foothills. Microsatellite markers were used to infer selfing or outcrossing for the developing acorns. The citizen scientists observed 148 insect visitors to tanoak flowers over 11.5 hours of observation (in 65 observation periods). Pollinator exclusion resulted in lower fruit set and higher rates of selfing. The data suggest that tanoak is primarily an insect-pollinated species, though some level of wind pollination is likely. There is a diverse community of insects visiting tanoak flowers. In order to understand the importance of tanoaks to the native insect community, future research needs to focus on identifying the composition of the insect community, and the extent to which they rely on tanoak pollen and nectar as a food source.
Top-cited authors
Jon E Keeley
Richard A. Minnich
  • University of California, Riverside
James Shevock
  • California Academy of Sciences
James H. Thorne
  • University of California, Davis
Sandy Harrison
  • University of Reading